This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. We investigated pathogenesis and transmissibility of SHIVSF162P3N (P3N) and the clone, whether the clone could fully recapitulate the in vivo replicative characteristics of the parental isolate. Both SHIVSF162P3N, (P3N) and the clone were mucosally transmissible, preferentially depleted memory CD4 T cells. Fifteen (15) animals were rectally challenged, 3 animals with P3N plus clone and 12 animals with the clone alone. Both virus infected rectally, 6/12 animals controlled the virus in the clone group, whereas one animals challenged with the mixture virus ( P3N and clone) was able to control the virus. Preliminary results indicate that both virus were transmitted mucosally with no significant difference in viral set points and progression to disease.